Monkey semantics: two ‘dialects’ of Campbell’s monkey alarm calls

Abstract

International audienceWe develop a formal semantic analysis of the alarm calls used by Campbell’s monkeys in the Tai forest (Ivory Coast) and on Tiwai island (Sierra Leone)—two sites that differ in the main predators that the monkeys are exposed to (eagles on Tiwai vs. eagles and leopards in Tai). Building on data discussed in Ouattara et al. (PLoS ONE 4(11):e7808, 2009a; PNAS 106(51): 22026–22031, 2009b and Arnold et al. (Population differences in wild Campbell’s monkeys alarm call use, 2013), we argue that on both sites alarm calls include the roots krak and hok, which can optionally be affixed with -oo, a kind of attenuating suffix; in addition, sentences can start with boom boom, which indicates that the context is not one of predation. In line with Arnold et al., we show that the meaning of the roots is not quite the same in Tai and on Tiwai: krak often functions as a leopard alarm call in Tai, but as a general alarm call on Tiwai. We develop models based on a compositional semantics in which concatenation is interpreted as conjunction, roots have lexical meanings, -oo is an attenuating suffix, and an all-purpose alarm parameter is raised with each individual call. The first model accounts for the difference between Tai and Tiwai by way of different lexical entries for krak. The second model gives the same underspecified entry to krak in both locations (= general alarm call), but it makes use of a competition mechanism akin to scalar implicatures. In Tai, strengthening yields a meaning equivalent to non-aerial dangerous predator and turns out to single out leopards. On Tiwai, strengthening yields a nearly contradictory meaning due to the absence of ground predators, and only the unstrengthened meaning is used

Formal monkey linguistics

“…These pertain to the inventory, use, structure, and sometimes phylogeny and ontogeny of various calls, in particular alert calls 2 -with rare cases of apparent dialectal variation (Schlenker et al 2014). Naturalistic observations make it possible to establish statistical correlations between (i) properties of the situations, such as the presence of predators or encounters between monkey groups, and (ii) calls used in those situations.…”

“…Further refinements were offered in later work. Adding to the picture, Schlenker et al (2014) discussed comparative data (due to Arnold and Keenan) suggesting that there is apparent dialectal variation between the Tai forest and Tiwai island: although krak has a primarily leopard-related meaning in Tai (where leopards exist), the same call is used as a general alert call on Tiwai, where leopards have been absent for decades. Schlenker et al (2014) developed several possible analyses, one of which posited that krak was a general alert call on both sites, hok was related to non-terrestrial disturbances, boom involved non-predation situations, and -oo had a (compositional) attenuative function.…”

“…Adding to the picture, Schlenker et al (2014) discussed comparative data (due to Arnold and Keenan) suggesting that there is apparent dialectal variation between the Tai forest and Tiwai island: although krak has a primarily leopard-related meaning in Tai (where leopards exist), the same call is used as a general alert call on Tiwai, where leopards have been absent for decades. Schlenker et al (2014) developed several possible analyses, one of which posited that krak was a general alert call on both sites, hok was related to non-terrestrial disturbances, boom involved non-predation situations, and -oo had a (compositional) attenuative function. The apparent dialectal variation was handled in this theory by positing that rules of competition among calls give rise to an optional enrichment of krak into something akin to krak and not hok and not krakoo; the resulting meaning was that of a 'serious terrestrial disturbance', which could single out leopards in Tai but would be essentially useless on Tiwai.…”

Formal monkey linguistics: The debate

“…Hence we should get the inference that a weak threat occurred, but not a nonground threat -hence presumably a ground threat. But our initial observation was that krak-oo is used as a completely general alert call, including in cases of eagle sightings (Ouattara's data: Ouattara et al 2009b;Schlenker et al 2014). The implicature of a non-ground threat thus does not seem to arise, thereby providing an argument within our preferred theory against analyzing -oo as an independent sentence.…”

Components of the Language-Ready Brain

“…14 There is evidence that some monkey species occasionally combine two calls to produce a modified meaning (Zuberbühler, 2002). These fairly limited phenomena are still poorly understood (for an intriguing pragmatic account, see Schlenker et al, 2014), but they hardly challenge the huge difference in compositionality between animal communication system and language (the only example of fairly sophisticated combinatoriality is birdsong, which, however, is not semantically compositional).…”